Above-grade flooring, despite the classy name, does not necessarily connote premium flooring. Rather than an indicator of quality, it is flooring that should only be installed at or above "the grade," or ground level.
Grade level is such an important issue when it comes to flooring because grade affects moisture content in an area. Flooring, in turn, is affected by moisture. Water can make its way down from grade-level to below grade when it rains. Groundwater can seek in through basement walls. Water can even slowly work upward through a concrete basement floor.
Special raised sub-floor panels like DRICore and Barricade can help mitigate below-grade moisture problems.
Flooring For Upstairs Only
Flooring that should be installed only on or above grade are always considered to be:
- Solid Hardwood: Hardwood easily warps and splits when subjected to moisture. Your expensive hardwood purchase will be wasted in a basement installation. Keep this upstairs. Some flooring rated as "above-grade" can, in a pinch, go below grade, but solid hardwood is not one of them.
- Cork: Cork is an organic product and as such is prone to rot. Cork is a wonderful floor covering for upstairs, though, as it is a sound dampening material.
- Carpeting (Organic Materials): Wool carpets beautifully grace upstairs rooms. Below grade they may rot or develop mold.
Flooring For Upstairs and Downstairs (Possibly)
At-risk flooring for basements are generally considered to be the following. These are floors that are routinely installed below-grade but can suffer irreparable damage upon contact with water. In the even of flooding, it is almost certain that all would need to be completely replaced.
- Carpeting (Manmade): Many flooring experts debate whether carpeting produced from manmade materials such as olefin or polyester can be used in basements. My view is that, as long as moisture is kept reasonably in check, it can be used. Of course, it may also be used above grade.
- Engineered Wood: Produced of organic materials that are considered dimensionally stable, engineered wood is not limited to above-grade applications only. It can tolerate some moisture downstairs, but not much of it.
- Laminate Flooring: Same as engineered wood, laminate flooring can take some water, but not too much of it. Laminate works well upstairs in dry areas, like living areas, bedrooms, and even in kitchens.
Flooring That Cannot Be Installed Upstairs
All floor coverings that are deemed perfect for basements--ceramic tile, porcelain tile, all forms of vinyl flooring, and natural stone--can be used above-grade.
Concrete is the only below-grade flooring that does not work upstairs due to weight limitations. Except in the case of an at-grade slab concrete floor, most residential structures that have a basement or crawlspace below cannot carry the weight of a concrete floor. Concrete floors built over an open area is a highly unusual building practice for most residences.
Making the Grade
Grading means little to homeowners who do not have a basement or any kind of floor sunken below ground level. For homes like this, any kind of flooring will suffice.
But once you start moving your living space below ground, strange things happen. Temperatures drop, sound deadens, moisture develops. The first two can be considered good or neutral things, but the third never is.
Below-grade moisture develops in many ways. It might come from obvious sources, such as leaking water supply or drain pipes, an overflowing washer, or faulty water heater. Or it can flow through cracks in the basement walls, due to ground water pressing against the foundation.
More often, though, moisture invisibly seeps upward through concrete flooring, dampening the bottom of your finish flooring. Warping, cracks, bends, and bows may happen and fungus and mold may develop. The only cure is to replace the floor.
Daylight basements are those which are built into a hill and that have one side sunken into the ground and the other side at-grade. Daylight basements sometimes have moisture problems because the "daylight" side can often be an invitation for water infiltration.
While raised subflooring like DRICore and Barricade can "unlock" this connection between finish flooring and moisture, the best solution is to have below-grade flooring that is not susceptible to moisture in the first place.